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I am having a problem when I connect my LG plasma tv (with a native resolution of 1024x768 pixels) to my 12.04 laptop using HDMI. The pixels (actual pixels, not the signal) of my TV are physically stretched so it gets his 16:9 ratio. In other words the pixels are rectangular (1.3333x1). Everything I display from my laptop oviously get stretched (4:3 stretched to 16:9).

There is a different dpi in X and Y needed for it to display properly (some kind of anamorphic mode). Default Ubuntu uses a dpi of 96x96. I can change it using xrandr, but only square eg 100x100 or 70x70.

Already looked here, but it seems Ubuntu totally ignore the displaySize in xorg.conf

When I use the code below to see the dpi and nothing I do changes it. The displaySize also stays the same (calculated using 96 dpi and the resolution)

xdpyinfo | grep -B2 resolution

I use the propretary ATI drivers for my ATI Mobility Radeon HD 50xx but it is the same with the Radeon drivers.

My temporary solution is to use:

xrandr --output DFP1 --mode 1024x768 --scale 1.333333333333x1 --output LVDS --off

But with this the right side of the screen is nog accesable. This is a known problem with xrandr --scale and ubuntu. This is because of a patch for the mouse/windows not going outside the screen.

I search a way to change the DisplaySize or the dpi(to something not square like 128x96) when I connect the display.

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This sounds like more of an issue with your TV than with Ubuntu. The scaling is happening in the TV hardware. Is there any particular reason you aren't using the natural resolution for your TV, rather than 1024x768? Perhaps outputting at 1920x1080 (assuming it's a 1080p TV) would be better? –  dobey Sep 21 '12 at 19:41
    
It is the resolution of my TV. That's why I have "non-square pixels" in the title. I can even see the pixels and count them if I want. There is no scaling in the TV. It's a budget 40" plasma. I know it is not a straight forward TV but I know it can. Just need to find how to set Ubuntu to use the screensize. Don't know what is keeping it from using it. –  labsin Sep 21 '12 at 20:35
    
@dobey Doing a bit of research with TVs, it seems that you need to adapt to non-square pixels in software, as TVs can have this and still have no problem. –  hexafraction Sep 22 '12 at 0:10
    
You didn't specify what laptop you have. Does it have HDMI output, or are you using VGA to connect the TV? –  dobey Sep 22 '12 at 2:11
    
It's a vaio VPCEB2E1E with a ATI Mobility Radeon HD 50xx (if it mathers I'll search the exact model) and connected with a HDMI-cable. –  labsin Sep 22 '12 at 13:41
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